In many cases, the power supply of electric circuits is achieved by DC/DC converters which are able to convert an input DC voltage to an output DC voltage being different from the input DC voltage. If a desired output voltage is higher than the input voltage, an up conversion has to be performed which is achieved, for example, by boost converters. If, however, the desired output voltage is lower than the input voltage, a down conversion has to be performed which is achieved, for example, by linear regulators or buck converters.
In some applications, both up and down conversion may be needed due to changing input or output voltages. Furthermore, for example for a fixed desired output voltage, which is to be derived from a battery powered input voltage, with a fully charged battery, a down conversion is needed, whereas after discharging of the battery, up conversion of the input voltage may be needed.
To this end, nowadays buck-boost converters are used being able to convert the input voltage up and down.
However, costs for implementing buck-boost converters are higher because of their more complicated structure and a higher area when implemented in an integrated circuit.